1. Field of the Invention
The present invention relates to a switch mechanism and a printer apparatus provided with the switch mechanism.
2. Description of the Background Art
One type of switch mechanism, typified by a push button, for example, allows a switch to be turned on and off by the switch being pushed. Such a switch is formed to allow internal contact points to be connected together when a button portion is pressed, and allow the contact points to be disconnected when the button portion ceases to be pressed. Alternatively, there exists a switch that allows contact points to be set to the connected state from the disconnected state when a button portion is pushed once, and allows the contacts points to be set to the disconnected state from the connected state when the button portion is pushed again.
In addition to the switch that allows an operation of an electrical device to be started and halted by a button being pressed repeatedly, a switch mechanism also includes a switch that senses a predetermined state. For example, there exists a so-called interlock switch in an electrical device having an open/close door. When sensing that the open/close door is brought into the opened state, the interlock switch controls an internal mechanism such that the internal mechanism is not operated while the open/close door is opened. Another switch mechanism is a limit switch in an automatic open/close door or the like. The limit switch senses a complete opened state or complete closed state of the automatic open/close door, and thereby halts the operation of opening or closing the open/close door.
Japanese Patent Laying-Open No. 7-282682 discloses a switch mechanism in which a buffer is provided at a support portion of a circuit board having a switch mounted thereon. In this switch mechanism, when a switch button is pushed, pushing force acts upon a tact switch, and thereby switching operation is completed. At this time, even if the pushing force is excessive or destructive, the buffer made of a spring connected to the circuit board allows the circuit board to translate in a direction along which the pushing force acts thereupon. It is disclosed that the tact switch is consequently prevented from being damaged.
Furthermore, Japanese Patent Laying-Open No. 6-89631 discloses a push button structure in which when a push button is pressed with a larger force than is necessary, a base plate having a tact switch fixed thereon translates in a direction along which the push button is moved. In this push button structure, an elastic hinge portion is formed at a tip of the base plate, and the base plate slides in a direction along which the push button is moved. It is disclosed that even if the push button is pushed more strongly than necessary and moved in more than a predetermined operating stroke, the switch can be prevented from being damaged.
In the switch mechanism that allows contact points to be connected and disconnected by a button portion being pressed, an excessive load may be applied to the switch mechanism temporarily or destructively, resulting in that the switch mechanism may be damaged. When a button portion is pushed with a finger, for example, an excessive pushing force may be applied and thereby cause damage to the switch mechanism. Alternatively, when an open/close door provided with an interlock switch is slammed shut, for example, a button portion may temporarily be pushed in more deeply than a position that corresponds to a closed position of the open/close door, and thereby cause damage to the switch mechanism.
In the switch mechanism disclosed in Japanese Patent Laying-Open No. 7-282682 or Japanese Patent Laying-Open No. 6-89631, a base plate itself, at which a tact switch that serves as a button portion is provided, is formed to translate. It is therefore necessary to place a main surface of the base plate to be in parallel to a direction along which the button is pushed, which inevitably increases the size of the switch mechanism.